66 



CORALS AND CORAL LSLANDS. 



tion of the stem enlarged, showing the cavities occupied by 

 the retracted polyps. 



In the genus Melitaea, and some others related, the inter- 

 nodes are porous and somewhat cork-like or suberous instead 



CORALI.RTM RUBRUM. 



of horny. The species of this group are often bright-coloured 

 and much brancherl, and resemble, in aspect, ordinary Gor- 

 gonicX ; but they are very brittle, breaking easily at the inter- 

 nodes. 



